High brightness solid state illumination system for fluorescence imaging and analysis

ABSTRACT

An illumination system includes a phosphor to emit light in a wavelength band Δλ PHOSPHOR , a second light source to emit light at a second wavelength λ 2  within an absorption band of the phosphor, a third light source to emit light at a third wavelength λ 3  and a fourth light source to emit light at a fourth wavelength λ 4 . A controller drives the second, third and fourth light sources. A first dichroic optical element: 1) directs light from the phosphor to an optical output of the system, 2) directs light from the third light source to the optical output, and 3) directs light from the fourth light source to the optical output. A second dichroic optical element: 1) directs light from the third light source to the first dichroic optical element, and 2) directs the light from the fourth light source to the first dichroic optical element.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of co-pending U.S. patentapplication Ser. No. 15/924,943, entitled High Brightness Solid StateIllumination System for Fluorescence Imaging and Analysis, which wasfiled on Mar. 19, 2018, which was a continuation of then co-pending U.S.patent application Ser. No. 14/862,492, entitled High Brightness SolidState Illumination System for Fluorescence Imaging and Analysis, whichwas filed on Sep. 23, 2015, said application is a continuation-in-part(CIP) of U.S. patent application Ser. No. 13/897,237, entitled HighBrightness Solid States Illumination System for Fluorescence Imaging andAnalysis, which was filed on May 17, 2013, which was related toco-pending U.S. patent application Ser. No. 13/900,089, filed May 22,2013, entitled “High Brightness Illumination System and WavelengthConversion Module for Microscopy and Other Applications”, which claimspriority from U.S. Provisional patent application Ser. No. 61/651,130,filed May 24, 2012. Each of these prior applications is incorporatedherein by reference in its entirety.

FIELD OF THE INVENTION

This invention relates to high brightness solid state illuminationsystems, particularly illumination systems for fluorescence imaging andanalysis.

BACKGROUND

High radiance illumination sources are required for fluorescence imagingand analysis, including fluorescence microscopy. Some applicationsrequire broadband or white light illumination. Other applicationsrequire relatively narrow band illumination of a particular wavelengthrange in the ultraviolet (UV), visible or infrared (IR) spectral region.

For example, conventional microscopy illumination systems typicallyutilize short arc lamps such as high pressure mercury, metal halide, andxenon lamps. These lamps are capable of very high radiance and aresuitable sources for direct coupled illumination systems, as well aslight guide coupled illumination systems, e.g. using a liquid lightguide or a fiber light guide. Nevertheless, it is recognized that thereare a number of problems associated with conventional lamp technologies,such as short lifetime, temporal variation of the output power, highvoltage operation (typically kilovolts are required to strike the lamp),and use of mercury. The latter is now seen as an environmental hazardand subject to regulations to limit use in numerous countries throughoutthe world.

Solid state light lighting technology has progressed significantly inrecent years and some high brightness light sources using solid stateLight Emitting Devices (LEDs), e.g. light emitting diodes, are nowavailable that can potentially provide sufficiently high radiance,broadband illumination for replacement of conventional arc lamps. Solidstate LED light sources can offer advantages over conventional arclamps, such as, much improved lifetime, lower cost of ownership, lowervoltage operation, lower power consumption (enabling some batteryoperated portable devices), and freedom from mercury. Additionally LEDlight sources can be readily controlled electronically, by modulatingthe current or voltage driving the device, which allows for fastswitching and intensity control through the LED driver, which can be asignificant advantage in many applications.

Nevertheless, despite technological advances in LED technology, highbrightness LED light sources are not available to cover all wavelengthsrequired for illumination systems for fluorescence imaging and analysis.In particular, the output of LED devices still do not match the radianceof traditional arc-lamps in some regions of the visible spectrum,especially in the 540 nm to 630 nm spectral band, i.e. in thegreen/yellow/amber range of the visible spectrum. The solid statelighting industry refers to this issue as the “green gap”. Emission inthis region of the spectrum is fundamentally limited by the lack ofavailability of semiconductor materials having a suitable band gap toproduce light of the required wavelength.

This is a particular problem for fluorescence imaging and analysis whichmay, for example, require illumination of a biological sample with arelatively narrow band of illumination of a particular wavelength thatis absorbed by a selected fluorophore or marker in the substance undertest.

For example, a traditional fluorescence illumination system, e.g. forfluorescence imaging or microscopy, comprises a short arc mercury lampwhich provides light emission having spectral peaks near 365 nm, 405 nm,440 nm, 545 nm and 575 nm. Standard fluorophores that are commonly usedfor fluorescence imaging and analysis are selected to have absorptionspectra having peaks optimized to match these lamp emission peaks. Toreplace a standard mercury lamp illuminator with a LED basedilluminator, it is desirable to be able to provide emission at the samewavelengths and with a comparable output power. There are suitablypowerful LEDs that are commercially available for emission at 365 nm,405 nm, 440 nm. However, in view of the “green gap” mentioned above,there are currently no single color, high brightness LEDs commerciallyavailable for emission at 545 nm and 575 nm.

It is well known in the art of LED lighting and illumination to use LEDsin combination with luminescent materials, i.e. fluorescent materials orphosphors, to generate light of wavelengths that are outside the rangeemitted directly by the LEDS, i.e. by wavelength conversion. Inparticular, a UV or blue light emitting LED may be combined with aremote or direct die-contact phosphor layer or coating to obtainbroadband light emission of a desired color temperature. For example, ablue light emitting diode or diode array with an emission peak in therange between 445 nm and 475 nm is combined with a phosphor layercomprising particles of Ce:YAG (cerium doped yttrium aluminum garnet)suspended in an encapsulant material such as silicone, which isdeposited directly on the LED. The blue light from the LED is absorbedby the phosphor and generates a broadband green/yellow/amber light whichcombines with the scattered blue light to produce a spectrum thatprovides the perception of white light. The overall brightness islimited by the blue light intensity from the LED and thermal quenchingof the phosphor, and the spectrum provides limited emission in regionsof the spectrum seen as green/yellow, approximately 560 nm and amber,approximately 590 nm.

Thus, relative to a mercury lamp, commercially available white lightLEDs that use a blue light emitting LED combined with a Ce:YAG phosphor,produce significantly weaker emission in the 545 nm and 575 nm regions.For example, at the objective plane of a microscope, output power at 545nm and 575 nm from such a white light LED was found to be about 10 timeslower than the output power from a mercury lamp. This level of power isinsufficient for most conventional fluorescence microscopy applications.

By increasing the drive current, some improvement of the light outputcan be achieved, but fundamentally, the power in this circumstance islimited by the maximum drive current density (i.e. current per unitarea) and factors, such as, the LED optical to electrical conversionefficiency, the LED output intensity, the phosphor quantum efficiency,and thermal quenching of both the LED and phosphor, as well as thecooling capacity. Even in the best case, the output from an overdrivenair cooled white LED is still 4 to 5 times less than a conventional lampwithin the 545 nm and 575 nm spectral range and the lifetime may besignificantly reduced by overdriving the device.

The following references provide some other examples of the use of LEDsources combined with fluorescent materials or phosphors in other forms.

U.S. Pat. No. 7,898,665 to Brukilacchio et al., issued Mar. 1, 2011,entitled “Light Emitting Diode Illumination System,” for example,discloses a system comprising an arrangement of multiple LEDS that arecoupled to a fluorescent rod which emits at a different wavelength toprovide sufficiently high brightness illumination for applications suchas microscopy or endoscopy. For example a single crystal of Ce:YAG maybe pumped by multiple LEDs to generate yellow or amber emission.However, the efficiency of such a device would be limited by totalinternal reflection due to the high index of refraction of Ce:YAG andrequires coupling of multiple LEDs to generate output of sufficientbrightness, which increases the cost, size, thermal and electricalrequirements.

To provide a more compact and efficient system, the above referencedrelated U.S. Patent application No. 61/651,130, discloses anillumination system that comprises a laser light source, e.g. providingblue light emission in the 440 nm to 490 nm range, for excitation of awavelength conversion module comprising a wavelength conversion medium,such as Ce:YAG crystal, of a particular shape and size, set in amounting for thermal dissipation, and an optical concentrator. The shapeand size of the wavelength conversion crystal, provides a compact lightsource with a configuration suitable for applications that require highbrightness and narrow bandwidth illumination at a selected wavelength,e.g. for fluorescence microscopy, or other applications requiringétendue-limited coupling or light guide coupling. While effective, dueto the particular shape and size of the crystal and coolingrequirements, this system is currently relatively costly to manufacture.A solution that is lower cost, compact and provides a broader spectrumis desirable for some applications.

Thus, there is a need for improved or alternative high radianceillumination sources, particularly those that can provide illuminationat wavelengths of 545 nm and 575 nm, for example, for fluorescenceimaging and analysis applications.

SUMMARY OF THE INVENTION

The present invention seeks to overcome or mitigate one or moredisadvantages of known high brightness illumination systems forfluorescence imaging and analysis, or at least provide an alternative.

Thus, one aspect of the present invention provides a method of providinghigh brightness illumination for fluorescence imaging and analysis,comprising: providing a first light source comprising a light emittingdevice (LED) and a phosphor layer, the LED emitting a first wavelengthλ₁ within an absorption band of the phosphor layer and the phosphorlayer emitting broadband light emission of longer wavelength comprisinglight in a wavelength band Δλ_(PHOSPHOR); providing a second lightsource comprising a laser emitting a second wavelength λ₂, within theabsorption band of the phosphor layer; and while operating the LED togenerate emission at λ₁ and Δλ_(PHOSPHOR), concurrently opticallypumping the phosphor layer with laser emission λ₂ to increase emissionintensity in the phosphor emission wavelength band Δλ_(PHOSPHOR). Insome implementations, the phosphor layer is optically pumped by the LEDor the laser, but not concurrently by both.

The method may comprise optically coupling emission comprising λ1 andΔλ_(PHOSPHOR), along a common optical axis, to an optical output. Themethod may comprise providing another light source emitting anotherwavelength λ₃, and optically coupling emission comprising λ₁,Δλ_(PHOSPHOR) and λ₃, along a common optical axis, to an optical output.

By way of example, the LED light source may comprise a standard whitelight emitting LED light source, i.e. comprising a blue light emittingLED emitting at wavelength λ₁ and a yellow Ce:YAG phosphor layer orcoating providing broadband emission over a wavelength bandΔλ_(PHOSPHOR). Typically, during normal operation of the blue lightemitting LED, the phosphor layer is not saturated by light from the blueLED. Thus, concurrent optical pumping of the phosphor layer with thelaser wavelength λ₂, within the absorption band of the Ce:YAG phosphorlayer, effectively increases the phosphor emission Δλ_(PHOSPHOR) in thegreen, yellow and amber regions of the spectrum.

In particular, the supplementary laser optical pumping of the phosphorprovides increased optical output over the emission band of thephosphor, so that sufficiently high radiance can be achieved at specificwavelengths, e.g. 545 nm and 575 nm, which are conventionally used forfluorescence imaging and analysis applications.

Another aspect of the present invention provides an illumination systemfor fluorescence imaging and analysis, comprising: a light source modulecomprising: a first light source comprising a first light emittingdevice (LED) and a phosphor layer, the first LED for providing emissionat a first wavelength λ₁ within an absorption band of the phosphor layerand the phosphor layer providing broadband light emission of longerwavelength comprising light in a wavelength band Δλ_(PHOSPHOR); a secondlight source for providing laser emission at a second wavelength λ₂,within the absorption band of the phosphor layer; a controller fordriving the first light source to generate emission at λ₁ andΔλ_(PHOSPHOR) and for concurrently driving the laser and opticallypumping the phosphor layer with the laser wavelength λ₂, to increaseemission in the emission band of the phosphor Δλ_(PHOSPHOR); and opticalcoupling means for coupling light emission to an optical output of theillumination system.

Thus a laser pumped LED light source unit or module is provided, whichhas a high radiance output in the emission band of the phosphorΔλ_(PHOSPHOR). The pump laser wavelength λ₂ may be the same as the LEDwavelength λ₁, or different from λ₁, provided it is within theabsorption band of the phosphor layer. The laser is preferably a solidstate laser, e.g. a laser diode, and the control unit provides LED/lasercontrollers and LED/laser drivers. A suitable choice of phosphor allowsfor an optical output with high brightness at particular wavelengths,e.g. for applications such as fluorescence imaging and analysis. Thephosphor layer may be selected to cover a band within the spectral rangefrom 350 nm to 750 nm and more particularly from 530 nm to 630 nm, i.e.within in the green gap.

In particular, this system provides for high brightness (i.e. highradiance) illumination, e.g., in the 545 nm and 575 nm bands, which arecommonly used for fluorescence imaging and analysis, such as, forfluorescence microscopy and for array slide scanners.

The optical coupling means comprises one or more optical elements suchas lenses or optical concentrators for focusing the laser emission ontothe phosphor layer, collecting emission at λ₁ and Δλ_(PHOSPHOR), andcoupling the emission at these wavelengths to the optical output of thelight source module.

For example, the optical coupling means comprises an optical element forcoupling the laser wavelength λ₂ to the phosphor layer for opticalpumping of the phosphor layer and for coupling emission from the firstLED and the phosphor layer, comprising λ₁ and Δλ_(PHOSPHOR), to theoptical output. Preferably the optical element comprises a dichroicelement that acts as a beam-splitter/combiner for coupling the laserwavelength λ₂ onto the phosphor layer for optical pumping of thephosphor layer and for coupling emission from the first LED and thephosphor layer, comprising λ₁ and Δλ_(PHOSPHOR), to the optical output.

If the pump laser wavelength λ₂ is less than the wavelength emission λ₁of the LED, in a preferred embodiment, the dichroic element has a bandedge λ_(D) greater than the laser wavelength λ₂, so that it reflects thelaser emission λ₂ and transmits output light emission comprising λ₁ andΔλ_(PHOSPHOR).

As an example, λ₁ comprises emission in the range from 445 nm to 475 nm,i.e. from a blue LED, and Δλ_(PHOSPHOR) covers the emission wavelengthrange from 500 nm to 750 nm. Preferably Δλ_(PHOSPHOR) covers theemission wavelength range from at least 530 to 630 nm (i.e. the “greengap”), and the pump laser wavelength λ₂ is 450 nm or less.

A dichroic beam-splitter/combiner, having a band edge wavelength λ_(D),between λ₁ and λ₂, may be positioned for reflecting the laser emissionλ₂ and transmitting output light emission comprising λ₁ andΔλ_(PHOSPHOR). For example, for wavelength ranges in the example above,if the pump laser wavelength λ₂ is 440 nm, and the blue LED emits λ₁ inthe range from 445 nm to 475 nm, the dichroic element has a band edgeλ_(D) of 443 nm.

The illumination system may further comprise one or more additionallight sources, e.g. at least one of a LED light source providing anemission wavelength λ₃ and an LED light source providing emission atwavelength λ₄. For example, these additional LED light sources areindividual LED light sources that provide outputs λ₃ and λ₄ in the nearUV and UV spectral regions, respectively. Optical coupling elements areprovided to couple outputs at these and other wavelengths, along acommon optical axis, to the optical output of the system.

Optical coupling elements may include a second dichroic element, i.e. adichroic beam-splitter/combiner, for combining outputs λ₃ and λ₄, andthen the first dichroic element combines λ₃ and λ₄ with λ₁ andΔλ_(PHOSPHOR). For example, the first LED has an emission band λ₁ in therange between 440 nm and 490 nm and more preferably between 445 nm and475 nm. The Δλ_(PHOSPHOR) band emitted by the phosphor layer is in therange from 500 nm to 750 nm and more preferably in the range from 530 nmto 630 nm. If the phosphor layer is Ce:YAG as described above, the laserwavelength λ₁ is preferably 450 nm or less, for optical pumping of thephosphor layer. The additional individual LED light sources provide λ₃comprising near UV emission in the range from 410 nm to 445 nm and λ₄comprising UV emission in the range from 370 nm to 410 nm or from 350 nmto 390 nm.

In this example, a second dichroic element having a band pass edgewavelength between λ₃ and λ₄, e.g. 409 nm, is used to combine these twowavelengths. Then, if the laser pump wavelength λ₂, and LED emission atλ₃ and λ₄, are all on the short wavelength side of the 443 nm band edgewavelength λ_(D) of the first dichroic element, this element combines λ₃and λ₄ with λ₁ and Δλ_(PHOSPHOR), along the primary optical axis, toprovide an optical output comprising each of these wavelengths.

Optionally the system may comprise one or more additional individual LEDlight sources and/or one or more additional light source modules forlight emission in other spectral bands. For example, additional lightsources may provide spectral bands that are in the ultraviolet and nearultraviolet region. These additional sources may comprise, e.g.: a UVLED emitting in the range from 350 nm to 390 nm, e.g. having a peak at365 nm; or a UV LED emitting in the range from 370 to 410 nm, e.g.having a peak at 385 nm; or a phosphor coated UV LED emitting in thenear UV range from 410 nm to 445 nm.

In one embodiment, the at least one additional light source or lightsource module comprises a LED providing emission at λ₄ and a phosphorlayer (Phosphor2) providing a broad emission band Δλ_(PHOSPHOR2). Forexample, if both λ₄ and Δλ_(PHOSPHOR2) lie on the same side (i.e. theshort wavelength side in the example above) of the band edge wavelengthλ_(D) of the first dichroic element, the dichroic element combines λ₄and Δλ_(PHOSPHOR2) with λ₁ and Δλ_(PHOSPHOR), to enable coupling of eachof these wavelength bands, along the primary optical axis, to theoptical output of the light source unit.

Typically, an optical filtering system within a fluorescence imagingsystem, such as a fluorescence microscope, provides for furtherfiltering of a selected wavelength band from the output of theillumination system.

If desired, the illumination system may also comprise one or moreadditional LED light source modules, providing other wavelength bands.It may comprise an additional laser pumped LED light source module, i.e.a second pump laser emitting a wavelength λ₅ within an absorption bandof a second phosphor layer (Phosphor2), for optically pumping the secondphosphor layer (Phosphor2). A second dichroic beam-splitter/combiner maybe provided, having a wavelength edge that is selected to reflect thelaser wavelength λ₅ and transmit the emission bands at λ₄ andΔλ_(PHOSPHOR2).

Another aspect of the present invention provides illumination system forfluorescence imaging and analysis, comprising: first and second lightsource modules and a controller;

the first light source module for providing emission in a firstwavelength band, comprising: a first light source comprising a first LEDand a first phosphor layer, the first LED providing emission at a firstwavelength λ₁ within an absorption band of the phosphor layer and thefirst phosphor layer providing broadband light emission Δλ_(PHOSPHOR1);a second light source comprising a laser emitting at a second wavelengthλ₂, within the absorption band of the first phosphor layer; wherein thecontroller concurrently drives the first light source to generateemission comprising λ₁ and Δλ_(PHOSPHOR1) and drives the laser foroptically pumping the first phosphor layer with the laser wavelength λ₂to increase emission in the emission band of the phosphorΔλ_(PHOSPHOR1);

the second module for providing emission in a second wavelength banddifferent from the first wavelength band, comprising: a third lightsource comprising second LED and a second phosphor layer different fromthe first phosphor layer, the second LED emitting at a wavelength λ₄within an absorption band of the second phosphor layer and the secondphosphor layer providing broadband light emission Δλ_(PHOSPHOR2); afourth light source comprising a laser emitting at a wavelength λ₅within the absorption band of the second phosphor layer; wherein thecontroller concurrently drives the second light source to generateemission comprising λ₄ and Δλ_(PHOSPHOR2) and the laser for opticallypumping the second phosphor layer with the laser wavelength λ₅ and thelaser wavelength λ₅, to increase emission in the emission band of thesecond phosphor Δλ_(PHOSPHOR2); and

optical coupling means comprising at least one dichroicbeam-splitter/combiner for coupling one or more of λ₁, Δλ_(PHOSPHOR1),λ₄ and Δλ_(PHOSPHOR2), along a common optical axis, to an optical outputof the illumination system.

The optical coupling means comprises optical coupling elements such as acoupling lens, an optical concentrator or other optics, and one or moredichroic elements having suitable passband, i.e. dichroicbeam-splitters/combiners, to enable the LED light sources and laserlight sources to be compactly arranged and for optically coupling thelight emission from the LEDs and the phosphor layers to the primaryoptical axis, aligned to the optical output of the illumination system.The optical coupling elements may comprise dichroic elements forsplitting and/or combining emission wavelengths from each light source,as required, and preferably first and second dichroicbeam-splitters/combiners having band edges selected for reflecting laserwavelengths λ₂ and λ₅, respectively.

An illumination system, according to preferred embodiments of theinvention, has the potential of meeting and exceeding the output of thebest arc lamps systems available today at particular wavelengths usedfor fluorescence microscopy, while overcoming at least some of thelimitations of existing high brightness LED light sources.

The foregoing and other objects, features, aspects and advantages of thepresent invention will become more apparent from the following detaileddescription, taken in conjunction with the accompanying drawings, ofpreferred embodiments of the invention, which description is by way ofexample only.

BRIEF DESCRIPTION OF DRAWINGS

In the drawings, identical or corresponding elements in the differentFigures have the same reference numeral, or corresponding elements havereference numerals incremented by 100 in successive Figures.

FIG. 1 illustrates schematically an illumination system comprising alight source module according to a first embodiment of the invention;

FIG. 2 illustrates schematically an illumination system comprising alight source module according to a second embodiment;

FIG. 3 shows spectral data for the light source module 100-1 illustratedin FIG. 2, without laser pumping and with laser pumping;

FIG. 4 shows experimental results comparing the optical output power ofthe light source module illustrated in FIG. 2, with and without laserpumping;

FIG. 5 illustrates schematically an illumination system according to athird embodiment, wherein a light source unit comprises a first lightsource module similar to that shown in FIG. 2, together with twoadditional LED light sources;

FIG. 6 illustrates schematically an illumination system according to afourth embodiment, wherein a light source unit comprises a first lightsource module similar to that shown in FIG. 2, together with a secondlight source module;

FIG. 7 shows an output spectrum of the second light source module shownin FIG. 6;

FIG. 8 illustrates schematically an illumination system according to afifth embodiment wherein the light source unit comprises a first lightsource module and a second light source module;

FIG. 9 shows the spectral output of the first and second light sourcemodules of FIG. 8: A. without laser pumping of either module, and B.with laser pumping of both modules;

FIG. 10 illustrates schematically an illumination system according to asixth embodiment, similar to that shown in FIG. 5, except that the pumplaser is coupled by a flexible fiber light guide to the first lightsource unit.

FIG. 11 shows a first arrangement of optical elements for couplingemission of one or more wavelengths, from a light source unit asillustrated in FIG. 5, along a primary optical axis to the opticaloutput of the illumination system;

FIG. 12 shows a second arrangement of optical elements for couplingemission of one or more wavelengths, from a light source unit asillustrated in FIG. 10, along a primary optical axis to the opticaloutput of the illumination system;

FIGS. 13A-C show three configurations of optical elements for couplingof the pump laser to the phosphor layer of the LED1 using respectively:13A. a lens; 13B. a Compound Parabolic Concentrator (CPC); and 13C. ataper;

FIG. 14 shows an arrangement of optical elements for coupling emissionof one or more wavelengths, from a light source unit as illustrated inFIG. 4, to an optical input of a fluorescence microscope system, using aliquid light guide;

FIG. 15 illustrates schematically an illumination system according toanother embodiment;

FIG. 16 illustrates schematically an illumination system according toyet another embodiment;

FIG. 17 illustrates schematically an illumination system according toeven another embodiment;

FIG. 18 illustrates schematically an illumination system according tostill another embodiment;

FIG. 19 is a chart showing a prophetic example of optical output vs.intensity setting in an exemplary illumination system with more than oneoperating mode;

FIG. 20 is a schematic representation of another exemplary illuminationsystem;

FIG. 21 is a detailed exemplary optical configuration of a light sourceunit, like the light source unit in FIG. 20;

FIG. 22 is a schematic representation of one exemplary alternativeconfiguration for providing laser light that may be used to pump thephosphor in any one of the light source units disclosed herein;

FIG. 23 is a schematic representation of another exemplary alternativeconfiguration for providing laser light that may be used to pump thephosphor in any one of the light source units disclosed herein;

FIG. 24 is a schematic representation of yet another exemplaryalternative configuration for providing laser light that may be used topump the phosphor in any one of the light source units disclosed herein;and

FIG. 25 is a side view of a tapered hexagonal rod, and shows the shapeand relative size of opposite ends of the tapered hexagonal rod.

DESCRIPTION OF PREFERRED EMBODIMENTS

A schematic diagram showing elements of an illumination system 1000,according to a first embodiment of the invention, is shown in FIG. 1.The illumination system 1000 comprises a light source unit or module 100for providing high brightness illumination for fluorescence illuminationand analysis. The light source unit 100 comprises first and second lightsources 110 and 120. The first light source 110 comprises an LED 112(LED1) and a phosphor layer 114, the LED 112 emitting a first wavelengthλ₁ within an absorption band of the phosphor layer and the phosphorlayer 114 emitting broadband light emission of longer wavelength,comprising light in a wavelength band Δλ_(PHOSPHOR) (abbreviated asΔλ_(P) in the Figures). The second light source 120 comprises a laser120 emitting at a second wavelength λ₂, also within an absorption bandof the phosphor layer. The illumination system 1000 also comprises drivemeans or drive unit, i.e. controller/driver 180 comprising a powersupply 182, LED/laser controller 184 and LED/laser drivers 186, whichare coupled by electrical connections 188 for concurrently driving theLED 110 and the laser 120, to enable optical pumping of the phosphorlayer 114 with the laser 120, i.e. at the laser wavelength λ₂.

As shown in FIG. 1, in a simple arrangement to provide for laser pumpingof the phosphor layer, the first and second light sources 110 and 120are arranged so that the laser 120 illuminates the phosphor layer 114 atan angle, e.g. at grazing incidence, and emission from the LED 112 andthe phosphor 114, comprising wavelengths λ₁ and Δλ_(PHOSPHOR), that isemitted along a primary optical axis A, is coupled to an optical output160 of the system. The laser 120 may be coupled to the phosphor layerthrough a light guide, an optical concentrator or other optical elements(not shown in FIG. 1).

The first light source 110 may be a phosphor coated LED, mounted on asuitable heatsink for thermal management, e.g. a phosphor LED whichprovides high brightness white light illumination, i.e. comprising ablue light emitting LED 112 having a deposited phosphor coating 114providing emission over a desired wavelength band Δλ_(PHOSPHOR) in thelonger wavelength visible range. Under normal operation of the firstlight source 110, even when the LED 112 is driven at higher current orvoltage (i.e. the maximum driving current is limited by a maximumdriving current density), the phosphor layer 114 is not saturated by theblue light emission from LED 112. Thus, supplementary optical pumping ofthe phosphor 114, using the pump laser 120, significantly increases theoptical output of the phosphor emission band Δλ_(PHOSPHOR). The pumplaser wavelength λ₂ may be the same or different from the LED wavelengthλ₁, provided it is also within the absorption band of the phosphor layer114.

Thus, under normal operation, without laser pumping, driving the LED 112generates light from the LED itself at wavelength λ₁ together withemission in the emission band of the phosphor Δλ_(PHOSPHOR). Byconcurrently optically pumping the phosphor with the laser wavelengthλ₂, the optical output in the emission band of the phosphorΔλ_(PHOSPHOR) is increased significantly, as will be further explainedbelow with reference to FIGS. 2, 3 and 4, and subsequent Figures.

A preferred arrangement for high brightness illumination systems forfluorescence imaging and analysis, comprises two or more light sourcemodules, i.e. providing different output wavelengths, and opticalelements for coupling outputs from the two or more light source modulesalong a primary optical axis to the optical output of the system.

Thus, a schematic diagram showing elements of an illumination system1000-1, according to a second embodiment of the invention, is shown inFIG. 2. The illumination system 1000-1 comprises a light source unit ormodule 100-1 for providing high brightness illumination for fluorescenceillumination and analysis. The light source unit 100-1 is similar tothat shown in FIG. 1, in that it comprises first and second lightsources 110 and 120. The first light source 110 comprises an LED 112(LED1) and a phosphor layer 114, the first LED 112 emitting at a firstwavelength λ₁ within an absorption band of the phosphor layer and thephosphor layer 114 emitting broadband light emission of longerwavelength, comprising light in a wavelength band Δλ_(PHOSPHOR)(abbreviated as Δλ_(P) in the Figures). The second light source 120comprises a laser 120, preferably a solid state laser diode, emitting ata second wavelength λ₂, also within an absorption band of the phosphorlayer. Also provided is a dichroic element, i.e. abeam-splitter/combiner, 116 (D1), which reflects the laser wavelength λ₂to couple the pump laser excitation to the phosphor layer, and transmitsλ₁ and Δλ_(PHOSPHOR). That is, for the arrangement shown in FIG. 2, thedichroic beam-splitter/combiner has a band edge λ_(D) between λ₁ and λ₂.Thus the combined emission from the LED 112 and the phosphor 114, λ₁ andΔλ_(PHOSPHOR), is coupled, along the primary optical axis A, to theoptical output 160. Optionally, another light source 100-2, i.e.comprising an LED 130 (LED3) emitting another wavelength band λ₃ may beprovided and the dichroic beam-splitter/combiner 116 is also used tocouple λ₃ to the primary optical axis.

Preferably, other optical coupling elements such as lenses or opticalconcentrators are also provided for more efficiently coupling the laseremission λ₂ to the phosphor, and for collecting the light emissionλ₁+Δλ_(PHOSPHOR), and coupling this light emission, to an optical output160 of the light source unit 100. However, for simplicity theseadditional optical elements are not shown in FIG. 2, and they will bedescribed in more detail below with reference to FIGS. 11 to 14. By wayof example only, the first light source 110 comprises, a low cost,commercially available “white light” solid state light source i.e. a“white light LED” comprising a phosphor layer 114 pumped by a blue lightLED 112, which is manufactured for the demands of general highbrightness lighting. One example is a PhlatLight® White LED manufacturedby Luminus Devices, which comprises a blue light emitting LED and aCe:YAG type phosphor coating that provides an emission spectrum, such asillustrated in FIG. 3, spectrum B. The spectrum comprises a strong bluelight peak in a first spectral region λ₁ at around 450 nm from LED1 anda broad emission band Δλ_(PHOSPHOR) from 500 nm to 700 nm at longerwavelengths that peaks in the 530 nm to 630 nm region of the spectrum.Thus under normal operation, i.e. when electrically driven at a suitablecurrent and voltage, the resulting light emission, λ₁ and Δλ_(PHOSPHOR),combines to provide a white light spectrum, spectrum B. Withsupplementary optical pumping by laser 120 at λ₂, i.e. at 440 nm asshown in spectrum C, in the absorption band of the phosphor (spectrumE), the laser pumped emission spectrum shows increased intensity in thebroad emission band Δλ_(PHOSPHOR) of the phosphor, as shown by spectrumA. That is, spectrum A comprises emission from LED1 at λ₁ at 445 nm to475 nm, at a similar intensity as in spectrum B, with a much strongerpeak Δλ_(PHOSPHOR) between 500 nm and 750 nm, peaking at around 530 nmto 630 nm.

FIGS. 3 and 4 demonstrate that under normal operation of this phosphorbased LED 110, even when driven at higher current or voltage (i.e. themaximum driving current is limited by a maximum driving currentdensity), the phosphor layer 114 is not saturated by the blue lightemission from LED 112. Thus, supplementary optical pumping of thephosphor 114 using the pump laser 120 significantly increases theoptical output Δλ_(PHOSPHOR) from the phosphor at longer wavelengths, asshown by comparing the emission spectra A and B, in FIG. 3. Inparticular, by selecting an appropriate phosphor LED 110, having aphosphor emission in the 500 nm to 700 nm range, and preferably having apeak in the range from 530 to 630 nm, high brightness illumination canbe provided at these wavelengths, i.e. even within the green gap.

FIG. 4 shows the optical output of light source module 100-1 as afunction of LED drive current with and without supplementary laseroptical pumping of the phosphor layer. That is, FIG. 4 compares theoptical power at the objective plane of a fluorescence imaging system,when operating the white light LED with and without laser pumping, usinga 40× objective and an excitation filter to provide an illumination bandfrom 545 nm to 575 nm. For operation at the maximum driving current,with laser pumping, the output of the light source unit 100 in thiswavelength band was increased 2-3 times at the maximum driving current,compared to operation of the same white light phosphor LED 110 withoutsupplementary laser pumping of the phosphor layer.

Thus, by way of example, the light source module 100-1 for illuminationsystem 1000-1 comprises a first light source 110 comprising the LED1 112emitting λ₁ in the range 445 nm to 475 nm having a phosphor 114 emittingΔλ_(PHOSPHOR) in the range 500 nm to 750 nm, which is pumped by thesecond light source 120 comprising the laser emitting λ₂ at 440 nm. Theband edge wavelength λ_(D) of the dichroic element is selected at 443nm, i.e. between λ₁ and λ₂, and arranged to reflect the laser wavelengthλ₂, and transmit λ₁ and Δλ_(PHOSPHOR). Thus, the optical output of theillumination module 100 comprises λ₁+Δλ_(PHOSPHOR).

Referring again to FIG. 2, optionally, if it is required to provideanother light source 100-2, i.e. comprising an LED 130 (LED3) emittinganother wavelength band λ₃, the dichroic beam-splitter/combiner 116provides a compact and convenient way to couple light of wavelength λ₃from LED 130 to the primary optical axis. As illustrated, the dichroicbeam-splitter/combiner 116 has a pass band edge selected to reflect thelaser emission at the laser wavelength λ₂, and transmit emission at λ₁from the LED 110 and Δλ_(PHOSPHOR) from the phosphor, and also reflectλ₃, the output emission comprises λ₁ and Δλ_(PHOSPHOR) and λ₃. Thus, thecombined optical output λ₁+Δλ_(PHOSPHOR), and optionally λ₃, of theillumination system can be coupled to the optical input of afluorescence imaging and analysis system, such as a slide scanner orfluorescence microscope, with suitable coupling optics (not shown inFIG. 2, see FIGS. 11 to 14). As is conventional, filters within thefluorescence imaging system provide for selection of appropriatewavelengths for broadband or narrowband illumination, e.g. standardwavelength bands for fluorescence analysis, just as they would be if aconventional lamp illumination system was used. Beneficially, the solidstate illumination system of the embodiment not only provides highradiance illumination at selected wavelengths, but also provides otheradvantages of solid state light sources over conventional lamps, i.e.electronic control of illumination parameters, such as, intensity andpulse duration.

An illumination system 2000 according to a third embodiment is shown inFIG. 5. The light source unit 200 comprises a first light source module100-1, comprising first and second light sources 110 and 120, identicalto module 100-1 shown in FIG. 2. Like parts are labeled with the samereference numerals in each Figure. Additionally, a second light sourcemodule 100-2 comprises two additional light sources 100-2 and 100-3,i.e. a LED or LED arrays 130 and 140 for light emission at otherwavelengths. A second dichroic element, i.e. beam-splitter/combiner 118is provided, which has a band edge selected to combine the output ofLED3 and LED4. That is, a LED 130 (LED3) provides light emission at λ₃,and a LED 140 (LED4) provides light emission at wavelength λ₄. Forexample, LED3 and LED4 may provide near ultraviolet (near UV) emissionand UV emission respectively.

The drive system 180 is similar to that shown in FIG. 1, comprising apower supply 182, LED/laser controller 184 and LED/laser drivers 186 fordriving each of the LED light sources, i.e. LEDs 110, 130 and 140 andlaser 120. The additional dichroic element 118 is provided for couplingthe output from the third and fourth light sources 130 and 140, and thencombining other wavelengths, via the first dichroic element 116, alongthe primary optical axis, to couple each of the combined wavelengths,λ₁, Δλ_(P), λ₃ and λ₄, to the output 160 of the light source unit 200.

For example, the first light source 110 may comprise a blue lightemitting LED 112 emitting a wavelength λ₁ in the range from 445 nm to475 nm, with a phosphor layer 114 emitting in Δλ_(PHOSPHOR) in the 530nm to 630 nm band. The second light source 120 comprises a laseremitting at λ₂, i.e. at 440 nm in the absorption band of the phosphorlayer 114, and the dichroic element 116 has a 443 nm edge, i.e. asdescribed with respect to the light source unit 100-1 shown in FIG. 2.To provide a combined UV/near UV illumination band, LED 130 comprises anear UV LED (LED3) providing near UV emission at λ₃, e.g. 410 nm to 445nm, and LED 140 comprises a UV LED (LED4) providing UV emission at λ₄,e.g. 370 nm to 410 nm or 350 nm to 390 nm. In the configurationillustrated in FIG. 5, the second dichroic element 118 is provided whichhas a band edge to reflect the shorter wavelength UV emission at λ₄ fromLED4 and transmit the longer wavelength emission λ₃ from LED3. Theemission λ₃+λ₄ is reflected by the first dichroic element 116 andredirected to the optical output 160. That is, LED3 and LED4 can coverwavelengths in the near UV and UV bands which are reflected by the firstdichroic element 116, i.e. wavelengths shorter than the 443 nm bandedge. Thus, the illumination system 2000 provides for high brightnessillumination covering the UV, near UV, blue, green, yellow and red, tothe near infrared regions. With suitable choices of λ₁, λ₂,Δλ_(PHOSPHOR), λ₃, λ₄, the system can provide sufficient intensity ateach wavelength commonly used for fluorescence imaging and analysis.

An illumination system 3000 according to a fourth embodiment is shown inFIG. 6. This system comprises a first light source module 100-1identical to unit 100-1 shown in FIG. 2 and module 100-1 shown in FIG.5. Thus, it comprises a first light source 110 comprising LED 112 (LED1)and its phosphor layer 114 (Phosphor1) and a second light sourcecomprising the pump laser 120, providing output emission at λ₁ andΔλ_(P1). The second light source 100-2 module comprises a LED 140 (LED4)and a different phosphor layer 124 (Phosphor2). For example, to providea UV and near UV band, LED 4 comprises a UV LED, providing UV emissionλ₄ at 370-410 nm or 350-390 nm, for exciting Phosphor2. Phosphor2provides a near UV emission band, Δλ_(P2), e.g. 410-445 nm. A sampleemission spectrum of the second illumination module, comprising λ₄ andΔλ_(P2), is shown in FIG. 7. As explained with reference to FIG. 5,since λ₄ and Δλ_(P2) are shorter than the 443 nm band edge of thedichroic element 116, they will be reflected and redirected to theoptical output 160 of the illumination unit.

An illumination system 4000 according to a fifth embodiment is shown inFIG. 8. An illumination unit 400 comprises first and second illuminationmodules 100-1 and 100-2. The first illumination module 100-1 isidentical to module 100-1 illustrated in FIGS. 2 and 5. The secondillumination module 100-2 is a similar laser pumped phosphor LED, i.e.phosphor LED 130, comprising LED 140 (LED4) emitting λ₄, phosphor layer124 (Phosphor2) emitting Δλ_(P2), and a pump laser 150 emitting laserwavelength λ₅. In this embodiment, to provide a UV and near UV band andλ₄ and Δλ_(P2), the light source module 100-2 comprises LED4 emitting ina UV band, e.g. 375-410 within an absorption band of Phosphor2, andPhosphor2 emitting in the near UV band, e.g. 410-445 nm. The dichroicelement 118 is positioned to reflect the pump laser emission at λ₅ andtransmit the LED4 emission at λ₄. That is, second dichroic element 118has a passband edge between the LED5 laser wavelength λ₅ and the LED4wavelength λ₄, e.g. 373 nm. The resulting output emission spectrum ofsystem 4000 is shown in FIG. 9: spectrum A: without laser pumping oflight source module 100-1 or 100-2; and spectrum B: with laser pumpingof both modules 100-1 and 100-2. These spectra demonstrate thesignificant increase in emission intensity of both Phosphor 1 andPhosphor2 emission, with laser pumping.

An illumination system 5000 according to a fifth embodiment, comprisinga light source unit 500 is illustrated in FIG. 10. This system issimilar to that shown in FIG. 5, and all like components are labeledwith the same reference numerals. This embodiment differs from thatshown in FIG. 5 in that the pump laser 120 (Laser2) is housed within thecontrol unit 180 instead of within the light source unit 500. The outputof the pump laser is coupled by a flexible light guide 190 to an input162 of the light source unit 500, and then directed by the dichroicelement 116 for pumping of the phosphor layer 114.

In each of the embodiments described above, the pump laser system 120may comprise a solid state laser, e.g. a single laser diode or a laserdiode array. Each LED light source may comprise a single LED or a LEDarray. The phosphor layer for LED1 is integrated with LED1, i.e. adirect die contact layer or coating deposited on LED1, or a phosphorsuspended in an encapsulant such as silicon, also in direct contact withLED1. The Phosphor2 layer for LED4 is similarly integrated with LED4. Ina variation of the module 100-2 shown in FIG. 6, Phosphor1 or Phosphor2may be a remote phosphor layer, e.g. a phosphor coating on a separatesubstrate, pumped by (non-laser) LED1 or LED4. While specificarrangements of dichroic elements, i.e. beam-splitters and combiners,have been described it will be appreciated that other arrangements ofthese elements can be provided. In particular the wavelengths of eachlight source element may be combined or split by suitable choices of thebandpass or band edge of each dichroic element.

To simplify optical coupling, it is preferable that each dichroicelement is selected to reflect the pump laser wavelengths, i.e. λ₂ orλ₅, in the embodiments described above. Additionally, to provide foreffective optical coupling of the pump laser to the phosphor layer andefficient collection of the light emission from each light source,optical coupling elements such as lenses or optical concentrators areused. For simplicity these elements are not shown in the precedingFigures. FIGS. 11 to 14 show further details for arrangements of theseoptical coupling elements, by way of example.

FIG. 11 shows an arrangement of optical coupling elements for the systemillustrated in FIG. 5. Like parts are labeled with the same referencenumerals. For thermal management, the phosphor LED 110 comprising LED112 (LED1) and phosphor layer 114 is mounted on a copper plate 119 whichis cooled by water or forced air. Focusing and collection opticscomprise lens 122, which collects light emission from the pump laser120. The pump laser light λ₂ is reflected from dichroic element 116, andcollected by collection lens 124 to focus the pump laser light λ₂ ontothe phosphor layer 114. Light emission at λ₁ and Δ_(PHOSPHOR) iscollected by collection lens 124, transmitted by the dichroic element116 and collimated by output coupling lenses 126 for coupling to theoptical output 160 of the illumination system, e.g. to an optical inputof a fluorescence imaging and analysis system or to an optical input ofa microscope (not shown). Emission from the LEDs 130 and 140 iscollected by lenses 132 and 142, respectively, and coupled through thesecond dichroic plate 118, the first dichroic plate 116 and the outputcoupling lenses 126 to the optical output 160.

FIG. 12 shows an arrangement of optical coupling elements for a systemsuch as illustrated in FIG. 10. This arrangement is similar to thatshown in FIG. 8, except that the pump laser 120 is housed externally ofthe light source unit, for example within the control unit 180 as shownin FIG. 8, and the pump laser radiation is coupled to an input 162 ofthe light source unit 500 via a flexible optical light guide 190.

FIGS. 13 A, B and C show three variants of the arrangement of opticalcoupling elements shown in FIG. 10. In FIG. 13B the coupling lens 124Aof FIG. 13A is replaced by a compound parabolic concentrator 124B, andin FIG. 13C a conical tapered concentrator 124C is used. Other opticalcoupling elements are similar to those shown in FIG. 11.

In various implementations (including those described throughout thisapplication), any one of these optical coupling elements (e.g., couplinglens 124A, compound parabolic concentrator 124B, or tapered concentrator124C, etc.) can positioned relative to the phosphor as shown in FIGS.13A, 13B, or 13C. More specifically, in any of the implementationsdisclosed herein, a coupling element (e.g., coupling lens 124A, compoundparabolic concentrator 124B, or conical tapered concentrator 124C, etc.)can be positioned adjacent to or in contact with the phosphor andarranged so that light being directed toward the phosphor (e.g., from apump laser) and light emitted by the phosphor passes through thecoupling element.

In some implementation, the optical coupling element may be anon-conical tapered concentrator, such as a tapered hexagonal or squarerod. One example of a tapered hexagonal rod is shown in FIG. 25. Morespecifically, FIG. 25 shows the tapered nature of the rod and thehexagonal shape of each end. Since the rod is tapered, one end (with adimension from one flat face to an opposite flat face of “A1”) isdimensionally smaller than the other end (with a dimension from one flatface to an opposite flat face of “A2”). In an exemplary implementation,a tapered rod (hexagonal or otherwise) may have a dimensional ratio ofA1/A2 of between 1/3 and 1/2, with a length of between 40 and 50millimeters.

In another variant of the optical coupling elements, shown in FIG. 14,the optical emission transmitted or reflected towards the optical outputis collected by output coupling lens 126 and focused onto the input ofan optical light guide 192, which may be a liquid light guide, forcoupling to an input coupling lens 128 of a fluorescence imaging system,such as a fluorescence microscope or slide scanner. Again, other opticalcoupling elements are similar to those shown in FIG. 11 and are labeledwith like reference numerals.

In summary, a solid state high radiance illumination source as disclosedherein is capable of providing for high intensity illumination at eachof a number of wavelengths commonly used for fluorescence analysis andimaging. The laser pumped LED and arrangement of optical componentsprovide for a compact light source unit that may comprise one or moreindividual LED light sources or LED light source modules, providingdifferent wavelength outputs. The system provides an alternative toconventional arc lamps, and addresses limitations of other availablesolid state LED light sources to provide high brightness at selectedwavelengths, particularly in the 530 nm to 630 nm range.

The high radiance solid state illumination system also providesadvantages over conventional lamp illumination sources, for example,allowing for electronic control of intensity and pulse generation asdisclosed in PCT International patent application no. PCT/CA2012/00446entitled “Light Source, Pulse Controller and Method for ProgrammablePulse Generation and Synchronization of Light Emitting Devices”.

FIG. 15 is a schematic representation of an exemplary illuminationsystem 6000 (e.g., for fluorescence imaging and/or analysis). The system6000 is similar in some ways to the system 2000 in FIG. 5. Theillustrated system 6000 has a control unit 180, a light source unit 200,and a user interface 181.

The light source unit 200 includes a first light source module 100-1(with a first light source 112, a phosphor light source 114, a secondlight source 120, and a first dichroic optical element (D1) 116), asecond light source module 100-2 (with a third light source 130), athird light source module 100-3 (with a fourth light source 140) and asecond dichroic element (D2) 118. Each of the first, second, third, andfourth light sources 112, 120, 130 and 140 in the illustratedimplementation is a light emitting diode (LED). Of course, in variousimplementations, any or all of these may be a different kind of lightsource. In some implementations, any or all of these may be a laser. Inone exemplary alternative configuration, the second light source 120 isa laser, while the first light source 112, the third light source 130,and the fourth light source 140 are light emitting diodes.

The control unit 180 has a power supply 182, a controller 184 anddrivers 186, which are coupled by electrical connections 188 to thelight source unit 200. The control unit 180 is generally adapted tocontrol the light source unit 200.

In various implementations, including the one shown in FIG. 15, thephosphor light source 114 is a physically attached to the first lightsource 112 (e.g., as a layer of phosphor applied to a surface of thefirst light source 112). In other implementations, the phosphor lightsource 114 is physically separate from the first light source 112. Ifphysically separate, the phosphor light source 114 may take the form ofa ceramic or single crystal phosphor substrate, for example.

The first light source 112 is configured to emit light at a firstwavelength λ₁ within an absorption band of the phosphor light source114. The second light source is configured to emit light at a secondwavelength λ₂ also within the absorption band of the phosphor lightsource 114. The third light source 130 is configured to emit light at athird wavelength λ₃. The fourth light source 140 is configured to emitlight at a fourth wavelength λ₄. The phosphor light source 114 isconfigured (e.g., when being pumped or excited) to emit light having awavelength in a wavelength band Δλ_(PHOSPHOR). In a typicalimplementation, the wavelength of light emitted by the phosphor lightsource 114 is longer than the first wavelength λ₁.

The controller 180 is configured to drive the first, second, thirdand/or fourth light sources, concurrently or otherwise. For example, insome implementations, the controller 180 is adapted to drive the firstlight source 112 and the second light source 120 to pump the phosphorlight source 114 concurrently. In some implementations, the controller180 is adapted to drive only one of the first light source 112 or thesecond light source 120 at a given time to pump the phosphor lightsource, without concurrently driving the other. For example, in oneimplementation, the controller 180 is adapted to drive the second lightsource 120 to optically pump the phosphor light source 114 withoutconcurrently driving the first light source 112 to optically pump thephosphor light source 114. In a typical implementation, one or more (orboth) of the third light source 130 and fourth light source 140 areconfigured to operate while the phosphor light source 114 is beingpumped.

The first dichroic optical element (D1) 116 in the illustratedimplementation is configured to: 1) direct light emitted by the secondlight source 120 at the second wavelength λ₂ onto the phosphor lightsource 114, 2) direct light emitted by the phosphor light source 114 inthe wavelength band Δλ_(PHOSPHOR) (and, optionally, light emitted by thefirst light source 112 at the first wavelength λ₁) to an optical output160 of the illumination system, 3) direct light emitted by the thirdlight source 130 at the third wavelength λ₃ to the optical output 160 ofthe illumination system, and 4) direct light emitted by the fourth lightsource 140 at the fourth wavelength λ₄ to the optical output 160 of theillumination system.

The second dichroic optical element (D2) 118 in the illustratedimplementation is configured to: 1) direct the light emitted by thethird light source 130 at the third wavelength λ₃ to the first dichroicoptical element (D1) 116, and 2) direct the light emitted by the fourthlight source 140 at the fourth wavelength λ₄ to the first dichroicoptical element (D1) 116.

Light emitted from each respective one of the first, second, third andfourth light sources 112, 120, 130, 140 follows a particular paththrough the illustrated light source unit 200. In this regard, lightfrom the first light source 112 (if energized) is directed onto thephosphor light source 114 and travels through the first dichroic opticalelement (D1) 116 to the optical output 160. Light from the second lightsource 120 is directed by the first dichroic light source (D1) 116 ontothe phosphor light source 114. Light from the phosphor light source 114travels through the first dichroic optical element (D1) 116 to theoptical output 160. Light from the third light source 130 travelsthrough the second dichroic optical element (D2) 118 and is thenreflected by the first dichroic optical element (D1) 116 to the opticaloutput 160. Light from the fourth light source 140 is reflected by thesecond dichroic optical element (D2) 118 toward the first dichroicoptical element (D1) 116 and is then reflected by the first dichroicoptical element (D1) 116 toward the optical output 160.

Thus, in the illustrated implementation, light from the third lightsource 130 and light from the fourth light source 140 travel between thefirst dichroic optical element (D1) 116 and the second dichroic opticalelement (D2) 118 along a first common optical path. Moreover, lightemitted by the first light source 112 (if the first light source 112 isenergized), light emitted by the phosphor light source 114, lightemitted by the second light source 120, light emitted by the third lightsource 130, and light emitted by the fourth light source 140 travel fromthe first dichroic optical element (D1) 116 to the optical output 160along a second common optical path.

In some implementations, the illustrated system is operable within andswitchable between multiple operating modes. These operating modes caninclude, for example, any two or more of the following: a firstoperating mode (e.g., a low power mode) in which only the first lightsource 112 is optically pumping the phosphor light source 114, a secondoperating mode (e.g., a medium power mode) in which only the secondlight source 120 is optically pumping the phosphor light source 114, anda third operating mode (e.g., a high power mode) in which the firstlight source 112 and the second light source 120 are concurrentlyoptically pumping the phosphor light source 114. In someimplementations, the illumination system is switchable between any orall three of these (and possibly more) operating modes.

If the system is operable within and switchable between multipleoperating modes, in general, the controller 180 typically implements anyswitching that happens. Moreover, in some implementations, the systemhas a user interface device 181 (e.g., a knob, toggle switch, touchscreen, etc.) that enables a user to specify which of the availableoperating modes (e.g., low power/intensity, medium power/intensity orhigh power/intensity) the system should be operating in. In theseimplementations, the controller 180 can be configured to implement theswitching in response to an instruction from the user interface device181. In some implementations, the system can be adapted to switchbetween available operating modes automatically (i.e., without specificinput from a human at the time of the switching). In theseimplementations, the switching may occur automatically in response to asoftware instruction, a timing signal, or the like.

FIG. 16 shows another exemplary illumination system 7000 that is in someways similar to system 6000 in FIG. 15. In system 7000 the second lightsource 120 is a pump laser (though it could, of course, alternatively,be an LED), and in system 7000 the phosphor light source 114 isphysically separate from the first light source 112.

FIG. 17 shows an exemplary illumination system 8000 that is similar insome ways to system 7000 in FIG. 16. In system 8000 there is no firstlight source (e.g., 120 in FIG. 16)—and the phosphor light source 114 isa physically stand-alone component. In the illustrated system 8000, onlythe second light source 120 is configured to pump the phosphor lightsource 114.

FIG. 18 shows an exemplary illumination system 9000 that is similar insome ways to system 6000 in FIG. 15. In system 9000, however, 1) thesecond light source 120 is a pump laser, 2) there are three (instead oftwo) dichroic optical elements: a first dichroic optical element (D1)116, a second dichroic optical element (D2) 118 and a third dichroicoptical element (D3) 119, and 3) there is an optical filter 121 betweenthe third 119 and first 116 dichroic optical elements. In a typicalimplementation, the optical filter 121 is configured to filter out aportion of light emitted by the phosphor light source 114—so that only aportion of the phosphor emission spectrum is combined with the otherwavelengths.

Due to the extra optical elements and the different overallconfiguration in system 9000 as compared to the system 6000 in FIG. 15,some of the optical light paths that the light from the different lightsources follow are somewhat different as well.

For example, in system 9000, light from the first light source 112 isdirected onto and pumps the phosphor 114, travels through the thirddichroic optical element 119, may be (or may not be) partially filteredby the optical filter 121 travels through the first dichroic opticalelement 116 and through the optical output 160. Light from the secondlight source 120 is reflected by the third dichroic optical element 119onto the phosphor 114 to pump the phosphor 114. Light from the thirdlight source 130 travels through the second dichroic optical element118, is reflected by the first dichroic optical element and travelsthrough the optical output 160. Light from the fourth light source 140is reflected by the second dichroic optical element 118 and reflectedagain by the first dichroic optical element 116 and then travels throughthe optical output 160.

In various implementations, one or more of the systems disclosed hereinmay be operable within and switchable between multiple operating modes.These operating modes can include, for example, any two or more of thefollowing: a first operating mode (e.g., a low power mode) in which onlya first light source 112 is optically pumping the phosphor light source114, a second operating mode (e.g., a medium power mode) in which only asecond light source 120 is optically pumping the phosphor light source114, and a third operating mode (e.g., a high power mode) in which thefirst light source 112 and the second light source 120 are concurrentlyoptically pumping the phosphor light source 114. An illumination systemmay be switchable between any or all three of these (and possibly more)operating modes.

If a system is operable within and switchable between multiple operatingmodes, in general, the controller 180 typically implements any switchingthat happens. Moreover, in some implementations, if the system has auser interface device (i.e., device 181 in FIGS. 15-18), the userinterface device enables a user to specify which of the availableoperating modes (e.g., low power/intensity, medium power/intensity orhigh power/intensity) the system should be operating in. In theseimplementations, the controller 180 can be configured to implementswitching in accordance with or in response to any instructions itreceives from the user via the user interface device (e.g., 181). Insome implementations, the system can be adapted to switch betweenavailable operating modes automatically (i.e., without specific inputfrom a human at the time of the switching). In these implementations,the switching may occur automatically in response to a softwareinstruction, a timing signal, or the like.

FIG. 16 is a chart showing a prophetic example of optical output vs.intensity setting (both represented by arbitrary units) in an exemplaryillumination system (whose first light source 112 is an LED and whosesecond light source 120 is a laser, such as shown in FIG. 8) with morethan one operating mode.

The chart in FIG. 16 includes information that relates to two operatingmodes: a first (lower optical output) operating mode, where only the LED112 is pumping the phosphor material 114, and a second (higher opticaloutput) operating mode, where only laser is pumping the phosphormaterial 114. In some implementations, the system might also have athird (even higher optical output) operating mode, where both the LED112 and the laser are pumping the phosphor material 114 concurrently(e.g., on opposite sides of the phosphor material 114).

As shown in the chart of FIG. 16, the transition between one operatingmode (e.g., the first (lower optical output) operating mode) and anotheroperating more (e.g., the second (higher optical output) operating mode)is substantially linear. In general, this linearity can be achieved byproperly calibrating the system (e.g., by ensuring that the usersettings correlate with drive currents for the LED and the laser suchthat the optical output, particularly when transitioning between twodifferent operating modes, is substantially linear).

In some implementations, the techniques and systems disclosed hereinfacilitate generating a relatively large amount of Yellow/Green lightwithout increasing the size of the light emitting area and mixing thiswith other discrete LED wavelengths to form a broad spectrum lightsource. In a typical implementation, Yellow light is generated in thephosphor layer (or component) after absorbing blue light, which may beinjected from the front of the layer (or component), from the back ofthe layer (or component), or from both. Also, in some implementations,pump 1 is LED1 and produces a Blue light, the Phosphor Layer is (butneed not be) part of LED1, and pump 2 is a laser that produces Bluelight. It has been found that, in practice, in some implementations,concurrently pumping the phosphor layer (e.g., with LED1 & a pump laser)may create a high heat load (e.g., on LED1—where the phosphor layer isintegrated with LED1) and for many applications the pump laser andphosphor layer provided enough optical power, even when LED1 is notoperational.

FIG. 20 is a schematic representation of an exemplary illuminationsystem 10000. The illustrated illumination system 10000 has a lightsource unit 200, a drive means or drive unit (i.e. controller/driver)180 for the light source unit 200, and a user interface 181.

The light source unit 200 in the illustrated implementation has aplurality of light emitting diodes (LEDs), including LED3, LED4, LED5,LED6, and LED7, a plurality of dichroic optical elements D1, D2, D3, D3,D4, D5, and D6, a phosphor light source 114, and a pump laser 120. In atypical implementation, the system 10000 also has a plurality of otheroptical elements (e.g., lenses, collimators, light guides, and thelike), which are not shown in FIG. 20.

During system 10000 operation, one or more (or, more typically, all) ofthe LEDs (LED3, LED4, LED5, LED6 and LED7) and the pump laser 120produce light, the dichroic optical elements (D1, D2, D3, D3, D4, D5,and D6), as applicable, collectively direct the light produced by theLED(s) and/or pump laser 120 and into a single system output.

In a typical implementation, each respective one of the LEDs (LED3,LED4, LED5, LED6 and LED7) and the pump laser 120 is configured toproduce light at a particular wavelength. More specifically, accordingto the illustrated implementation, LED3 is configured to produce lightat one wavelength λ₃, LED4 is configured to produce light at anotherwavelength λ₄, LED5 is configured to produce light at yet anotherwavelength λ₅, LED6 is configured to produce light at still anotherwavelength λ₆, LED7 is configured to produce light yet anotherwavelength λ₇, and the pump laser 120 is configured to produce light atwavelength λ₂. In a typical implementation, each of these wavelengths(λ₂, λ₂, λ₄, λ₅, λ₆, and λ₇) is different than the others. However, insome implementations, some of those wavelengths may be the same orsimilar to others.

In a typical implementation, the phosphor light source 114 is configuredto fluoresce at a wavelength λ_(phosphor) when optically stimulated (orpumped) by the pump laser. In a typical implementation, the lightproduced by the pump laser 120, at wavelength λ₂, is within anabsorption band of the phosphor light sources 114.

During system 10000 operation, light produced by the pump laser, atwavelength λ₂, is reflected off of dichroic optical element D3 towardthe phosphor light source 114. This light, at wavelength λ₂, causes thephosphor light source 114 to fluoresce, at wavelength λ_(phosphor). Thelight from the phosphor light source 114, at wavelength λ_(phosphor),passes through dichroic optical element D3, is reflected off dichroicoptical element D4, and passes through dichroic optical element D1 tothe system output. Light from LED5, at wavelength λ₅, is reflected offdichroic optical element D5, passes through dichroic optical elements D4and D1 to the system output. Light from LED6, at wavelength λ₆, passesthrough dichroic optical elements D5, D4, and D1 to the system output.Light from LED3, at wavelength λ₃, passes through dichroic opticalelement D2, and is reflected off dichroic optical element D1 to thesystem output. Light from LED7, at wavelength λ₇, is reflected offdichroic optical elements D6, D2, and D1 to the system output. Lightfrom LED4, at wavelength λ₄, passes through dichroic optical element D6,and is reflected off dichroic optical elements D2 and D1 to the systemoutput.

The system 10000 is configured, therefore, such that when all of theLEDs, the pump laser 120, and the phosphor light source 114 are emittinglight, the light exiting the system output is a combination of all thelight produced by all of the LEDs and the phosphor light source 114.Moreover, when any sub-group of the LEDs, the pump laser 120, and thephosphor light source 114 are emitting light, the light exiting thesystem output is a combination of all the light being produced by theLED(s) and/or phosphor light source 114 that are emitting light.

The control unit 180 in the illustrated implementation has a powersupply 182, an LED/laser controller 184, and LED/laser drivers 186. Thepower supply 182 is generally configured and operable to provide powerto other components including, for example, the LED/laser controller 184and/or the LED/laser drivers 186. The LED/laser drivers 186 are coupledby electrical connections 188 to the LEDs and to the pump laser 120 inthe light source unit 200. The LED/laser drivers 186 are configured todrive (concurrently or otherwise) every one of the LEDs and the pumplaser 120 in the light source unit 200. The LED/laser controller 184 isgenerally configured to control operation of the LED/laser drivers 186.

In some implementations, if the system 10000 is operable within andswitchable between multiple operating modes (e.g., a low power/intensitymode, a medium power/intensity mode, or a high power/intensity mode), ingeneral, the controller 180 may cause switching between those operatingmodes. In one exemplary implementation, a low power/intensity mode mightcall for only one or more (but less than all) of the light emittingcomponents in the light source unit 200 to be operational and,therefore, emitting light. In one exemplary implementation, a highpower/intensity mode might call for all of the light emitting componentsin the light source unit 200 to be operational and, therefore, emittinglight. In one exemplary implementation, a medium power/intensity modemight call for operating more light emitting components than the lowpower/intensity mode calls for, but operating fewer light emittingcomponents than the high power/intensity mode calls for.

In some implementations, the user interface 181, which may be a knob,toggle switch, touch screen, etc., enables a user to specify which ofthe available operating modes (e.g., low power/intensity, mediumpower/intensity or high power/intensity) the system 10000 should beoperating in. In these implementations, the controller 180 can beconfigured to implement the switching in response to an instruction fromthe user interface device 181. In some implementations, the system canbe adapted to switch between available operating modes automatically(i.e., without specific input from a human at the time of theswitching). In these implementations, the switching may occurautomatically in response to a software instruction, a timing signal, orthe like, sometimes without any contemporaneous input from a human userwhatsoever. In various implementations, the user interface 181 mayprovide a user with other ways to access, view and/or enter informationinto the system.

Thus, it can be seen that, in the implementation represented in FIG. 20,the first dichroic optical element D1 is configured to at least directthe light emitted by the phosphor light source 114 at wavelengthλ_(phosphor) to the optical output of the illumination system 10000.More particularly, in the illustrated implementation, this light,emitted by the phosphor light source 114 at wavelength λ_(phosphor),passes through the third and fourth dichroic optical elements D3 and D4first before reaching the first dichroic element D1, but then isdirected, by the first dichroic optical element D1, to the opticaloutput of the illumination system 10000.

Moreover, in the implementation represented in FIG. 20, the firstdichroic optical element D1 is configured to direct light emitted by thethird light source LED3 at the third wavelength λ₃ to the optical outputof the illumination system 10000. In this regard, the light emitted bythe third light source LED3 first passes through the second dichroicoptical element D2, but then is directed, by the first dichroic opticalelement D1, to the optical output of the illumination system 10000.

Additionally, in the implementation represented in FIG. 20, the firstdichroic optical element D1 is configured to direct light emitted by thefourth light source LED4 at the fourth wavelength λ₄ to the opticaloutput of the illumination system 10000. In this regard, the lightemitted by the fourth light source LED4 first passes through the sixthdichroic optical element D6 and is reflected off the second dichroicoptical element D2, but is then directed, by the first dichroic opticalelement D1, to the optical output of the illumination system 10000.

Moreover, in the implementation represented in FIG. 20, the seconddichroic optical element D2 is configured to direct light emitted by thethird light source LED3 at the third wavelength λ₃ to the first dichroicoptical element D1, and to direct light emitted by the fourth lightsource LED4 at the fourth wavelength λ₄ to the first dichroic opticalelement D1. In this regard, the light emitted by the fourth light sourceLED4 first passes through the sixth dichroic optical element beforereaching the second dichroic optical element D2.

The various light emitting components in the illustrated light sourceunit 200 can be adapted to emit light at various wavelengths. In onespecific exemplary implementation, λ₂ (from pump laser 114) is 450nanometers, λ₃ (from LED3) is 475 nanometers, λ₄ (from LED4) is 430nanometers, λ₅ (from LED5) is 635 nanometers, λ₆ (from LED6) is 735nanometers, λ₇ (from LED7) is 385 nanometers, Δλ_(phosphor) (the rangeof wavelengths from phosphor light source 114) is 500-600 nanometers.

In this specific exemplary implementation, dichroic optical element D3may be configured to transmit λ_(phosphor) (from phosphor light source114), which is 500-600 nanometers, but reflect 445-460 nanometers (e.g.,a range that would include the light emitted by pump laser 120, at λ₂(e.g., 450 nanometers)).

One detailed exemplary optical configuration of a light source unit,like the light source unit 200 in FIG. 20, is shown in FIG. 21.

The optical configuration of the light source unit 200 in FIG. 21 has aplurality of light emitting diodes (LEDs) including LED3, LED4, LED5,LED6, and LED7, a plurality of dichroic optical elements D1, D2, D3, D3,D4, D5, and D6, a tapered optical rod TR, a phosphor light source 114, apump laser 120 (e.g., an array of laser diodes), and a plurality ofother optical elements, including optical elements OE1, OE2, OE3, OE4,OE5, OE6, OE7, OE8, and OE9. In the illustrated implementation, opticalelements OE1 and OE2 are configured such that light from the pump laser120 passes through optical elements OE1 and OE2 before reaching dichroicD3. Also, in the illustrated implementation, optical element OE3 isconfigured such that light from the phosphor, that has passed throughthe tapered optical rod TR and dichroic D3 then passes through opticalelement OE3. Moreover, in the illustrated implementation, opticalelement OE4 is configured such that light from LED 5 passes throughoptical element OE4 before reaching dichroic D5. Additionally, in theillustrated implementation, optical element OE5 is configured such thatlight from LED 6 passes through optical element OE5 before it reachesdichroic D5. Also, in the illustrated implementation, optical elementOE6 is configured such that light from LED 4 passes through opticalelement OE6 before it reaches dichroic D6. Additionally, in theillustrated implementation, optical element OE7 is configured such thatlight from LED 7 passes through LED 7 before it reaches dichroic D6.Moreover, in the illustrated implementation, optical element OE8 isconfigured such that light from LED 3 passes through optical element OE8before it reaches dichroic D2. Finally, in the illustratedimplementation, optical element OE9 is configured such that light passesthrough optical element OE9 before passing into a light pipe LP at theoutput of the light source unit 200.

In various implementations, each optical element OE1, OE2, OE3, OE4,OE5, OE6, OE7, OE8, and OE9 may be configured to perform any one or moreof a variety of different optical functions. These optical functions mayinclude, for example, collimating, focusing, mixing, etc. As an example,in a typical implementation, including the implementation shown in FIG.21, optical elements OE1 and OE2 are configured to collimate and focus.Further, in a typical implementation, the light pipe LP, which can beany kind of integrating rod, taper or light mixer, helps produce betterspatial and color uniformity in light exiting the illustrated lightsource unit 200. In cross-section, the light pipe LP can have any one ofa variety of different shapes including, for example, rectangular,square, hexagonal, etc. The light pipe LP acts as an optical elementalong the common optical path to collect and mix all wavelengths.Another example of this kind of light pipe is identified as item 192 inFIG. 14. The light pipe could be a combination of a hexagonalhomogenizing rod+a liquid light guide or fiber light guide.

In some implementations, the pump laser 120 and collimating and focusingoptics OE1, OE2, in the light source unit 200 of FIG. 21 (and/or thepump laser in other light source units disclosed herein), may bereplaced with an alternative configuration for providing laser lightthat may include, for example, an array of laser diodes, or a pluralityof linear laser diodes (either directly coupled to an integrated opticalrod, or indirectly coupled to an integrated optical rod through one ormore mirrors). The tapered optical rod TR can be similar to the element124 c in FIG. 13C, and can have any cross-sectional shape (e.g.,circular, rectangular, hexagonal, etc.).

FIG. 22 is a schematic representation of one exemplary alternativeconfiguration for providing light (e.g., laser light and/or light withinan absorption band of the phosphor light source) that may be used topump the phosphor in any one of the light source units disclosed herein.The alternative source of laser light in the illustrated implementationincludes a 4 by 5 array of laser diodes, together with collimating andfocusing optics. Each laser diode in the illustrated array is configuredto direct its light into the collimating and focusing optics. If thisalternative configuration for providing laser light were placed into thelight source unit 200 of FIG. 21 in place of the pump laser shown inFIG. 21, then the light exiting the collimating and focusing opticswould head towards dichroic D3.

FIG. 23 is a schematic representation of another exemplary alternativeconfiguration for providing laser light that may be used to pump thephosphor in any one of the light source units disclosed herein. Thealternative source of laser light in the illustrated implementationincludes multiple laser diodes, with an integrated rod, together withcollimating and focusing optics. More specifically, the illustratedconfiguration includes two linear laser diodes, side-by-side, andoptically (and, optionally, physically) coupled to the integrated rod.The integrated rod, which may be, for example, a light pipe or waveguideis configured to receive the output light from each respective one ofthe laser diodes. After passing through the integrated rod, the lightpasses into the collimating and focusing optics If this alternativeconfiguration for providing laser light were placed into the lightsource unit 200 of FIG. 21 in place of the pump laser shown in FIG. 21,then the light exiting the collimating and focusing optics would headtowards dichroic D3.

FIG. 24 is a schematic representation of yet another exemplaryalternative configuration for providing laser light that may be used topump the phosphor in any one of the light source units disclosed herein.The alternative source of laser light in the illustrated implementationincludes multiple laser diodes, a plurality of mirrors, and anintegrated rod, together with collimating and focusing optics. Morespecifically, the illustrated configuration includes three laser diodes,arranged side-by-side relative to one another (though otherconfigurations are possible), and optically coupled, via the pluralityof mirrors, to the integrated rod. More specifically, light from eachlaser diode is directed to a corresponding one of the mirrors, whichreflects the light into the integrated rod, which may be, for example, alight pipe or waveguide. After passing through the integrated rod, thelight passes into the collimating and/or focusing optics. If thisalternative configuration for providing laser light were placed into thelight source unit 200 of FIG. 21 in place of the pump laser shown inFIG. 21, then the light exiting the collimating and focusing opticswould head towards dichroic D3.

Although embodiments have been described in detail above by way ofexample, it will be apparent that modifications to the embodiments maybe made. For example, each LED light source referred to as a LED, and itis apparent that each may be a single LED or an LED array of multipleLED, and the phosphor layer may be directly coated on the emittersurface of the LED or LED array, or provided as an overlying phosphorcontaining layer. For simplicity single optical elements such as lensesare illustrated, but compound lens or other suitable coupling optics maybe used. It will also be apparent that additional LED light sources maybe added and similarly optically coupled to the optical output usingoptical coupling elements comprising dichroic beam-splitter/combiners.However, to reduce reflective and transmissive losses, and reduce sizeand cost, it may desirable to provide a simple design with fewercomponents.

Additionally, various features from different implementations describedherein may be combined in ways not explicitly shown in the drawings orotherwise described explicitly.

The wavelengths and/or wavelength ranges indicated in this descriptionshould not be construed as limiting examples. The wavelengths andwavelength ranges indicated herein may vary.

Although embodiments of the invention have been described andillustrated in detail, it is to be clearly understood that the same isby way of illustration and example only and not to be taken by way oflimitation, the scope of the present invention being limited only by theappended claims.

What is claimed is:
 1. An illumination system comprising: a phosphorlight source configured to emit light having a wavelength in awavelength band Δλ_(PHOSPHOR); a second light source configured to emitlight at a second wavelength λ₂ within an absorption band of thephosphor light source; a third light source configured to emit light ata third wavelength λ₃; a fourth light source configured to emit light ata fourth wavelength λ₄; a controller configured to drive the secondlight source, the third light source and the fourth light source; afirst dichroic optical element configured to: 1) direct light from thephosphor light source in the wavelength band Δλ_(PHOSPHOR) to an opticaloutput of the illumination system, 2) direct light from the third lightsource at the third wavelength λ₃ to the optical output of theillumination system, and 3) direct light from the fourth light source atthe fourth wavelength λ₄ to the optical output of the illuminationsystem; and a second dichroic optical element configured to: 1) directthe light from the third light source at the third wavelength λ₃ to thefirst dichroic optical element, and 2) direct the light from the fourthlight source at the fourth wavelength λ₄ to the first dichroic opticalelement, wherein the second light source comprises more than one laser.2. The illumination system of claim 1, wherein the first dichroicoptical element is further configured to direct light emitted by thesecond light source at the second wavelength λ₂ onto the phosphor lightsource.
 3. The illumination system of claim 1, further comprising afirst light source configured to emit light at a first wavelength λ₁onto the phosphor light source.
 4. The illumination system of claim 3,wherein the phosphor light source is physically attached to the firstlight source.
 5. The illumination system of claim 3, wherein thephosphor light source is physically separate from the first lightsource.
 6. The illumination system of claim 5, wherein the phosphorlight source is a ceramic phosphor or a single crystal phosphor.
 7. Theillumination system of claim 3, wherein the wavelength of the lightemitted by the phosphor light source is longer than the first wavelengthλ₁.
 8. The illumination system of claim 3, wherein the controller isfurther configured to drive the first light source.
 9. The illuminationsystem of claim 3, wherein the first dichroic optical element is furtherconfigured to direct light emitted by the first light source at thefirst wavelength λ₁ along with the light emitted by the phosphor lightsource in the wavelength band Δλ_(PHOSPHOR) to the optical output of theillumination system.
 10. The illumination system of claim 3, wherein thefirst, third and fourth light sources are light emitting diodes.
 11. Theillumination system of claim 3, wherein the controller is configured todrive the second light source to optically pump the phosphor lightsource without concurrently driving the first light source to opticallypump the phosphor.
 12. The illumination system of claim 3, wherein thelight emitted by the first light source at the first wavelength, thelight emitted by the phosphor light source in the wavelength bandΔλ_(PHOSPHOR), the light emitted by the second light source at thesecond wavelength, the light emitted by the third light source at thethird wavelength, and the light emitted by the fourth light source atthe fourth wavelength travel from the first dichroic optical element tothe optical output along a common optical path.
 13. The illuminationsystem of claim 3, wherein the illumination system is switchable betweentwo or more of the following operating modes: a first operating mode inwhich only the first light source is energized to optically pump thephosphor light source; a second operating mode in which only the secondlight source is energized to optically pump the phosphor light source;and a third operating mode in which the first light source and thesecond light source are energized to optically pump the phosphor lightsource.
 14. The illumination system of claim 13, wherein theillumination system is switchable between all three of the operatingmodes.
 15. The illumination system of claim 13, wherein the controlleris configured to implement any of the switching between the operatingmodes.
 16. The illumination system of claim 15, further comprising auser interface device, wherein the controller is configured to implementthe switching in response to an instruction from the user interfacedevice.
 17. The illumination system of claim 3, wherein the phosphorlight source is configured to emit light in the wavelength bandΔλ_(PHOSPHOR) only in response to first absorbing light from the firstor second light sources.
 18. The illumination system of claim 1, whereinthe second light source is a laser.
 19. The illumination system of claim1, wherein the second light source is a light emitting diode.
 20. Theillumination system of claim 1, wherein the light emitted by the thirdlight source at the third wavelength λ₃ and the light emitted by thefourth light source at the fourth wavelength λ₄ travel between the firstdichroic optical element and the second dichroic optical element along acommon optical path.
 21. The illumination system of claim 1, wherein themore than one laser diode are arranged as an array of laser diodes. 22.The illumination system of claim 1, wherein the second light sourcefurther comprises optics configured to collimate and/or focus light fromthe laser diodes in the array of laser diodes.
 23. The illuminationsystem of claim 1, wherein the second light source further comprises anintegrated rod.
 24. The illumination system of claim 23, wherein theintegrated rod is a light pipe or waveguide configured to receive lightfrom each respective one of the more than one laser diode.
 25. Theillumination system of claim 23, further comprising optics forcollimating and/or focusing light from the more than one laser diodethat has passed through the integrated rod.
 26. The illumination systemof claim 1, wherein the second light source further comprises more thanone mirror.
 27. The illumination system of claim 26, further comprising:an integrated rod; and optics.
 28. The illumination system of claim 27,wherein light from each respective one of the laser diodes is directedto a corresponding one of the mirrors, which reflect the light towardthe integrated rod, wherein after passing through the integrated rod,the light passes into the collimating and/or focusing optics.
 29. Theillumination system of claim 1, wherein the second light source directslight towards a third dichroic optical element.
 30. An illuminationsystem comprising: a phosphor light source configured to emit lighthaving a wavelength in a wavelength band Δλ_(PHOSPHOR); a second lightsource configured to emit light at a second wavelength λ₂ within anabsorption band of the phosphor light source; a third light sourceconfigured to emit light at a third wavelength λ₃; a fourth light sourceconfigured to emit light at a fourth wavelength λ₄; a controllerconfigured to drive the second light source, the third light source andthe fourth light source; a first dichroic optical element configuredto: 1) direct light from the phosphor light source in the wavelengthband Δλ_(PHOSPHOR) to an optical output of the illumination system, 2)direct light from the third light source at the third wavelength λ₃ tothe optical output of the illumination system, and 3) direct light fromthe fourth light source at the fourth wavelength λ₄ to the opticaloutput of the illumination system; and a second dichroic optical elementconfigured to: 1) direct the light from the third light source at thethird wavelength λ₃ to the first dichroic optical element, and 2) directthe light from the fourth light source at the fourth wavelength λ₄ tothe first dichroic optical element; and an optical coupling elementadjacent to or in contact with the phosphor light source.
 31. Theillumination system of claim 30, wherein the optical coupling element isarranged so that light being directed toward the phosphor light sourceand the light emitted by the phosphor light source passes through theoptical coupling element.
 32. The illumination system of claim 30,wherein the optical coupling element is selected from the groupconsisting of a coupling lens, a compound parabolic concentrator, and atapered concentrator or homogenizing rod.
 33. The illumination system ofclaim 32, wherein the optical coupling element is a tapered concentratoror homogenizing rod having opposite ends with a dimensional ratio ofA1/A2 of between 1/3 and 1/2 and with a length of between 40 and 50millimeters.